Whole-lake silver nanoparticle addition promotes phosphorus and silver excretion by yellow perch ( Perca flavescens )

Fish excretion supports primary production by supplying essential nutrients. However, our understanding of how contaminants affect fish nutrient excretion rates and contaminant persistence in aquatic environments is limited. This is relevant for contaminants like silver nanoparticles (AgNP), increasingly found in aquatic environments due to industrial use and runoff. We investigated the effect of chronic exposure to AgNP under environmentally relevant conditions on yellow perch ( Perca flavescens) nutrients and silver (Ag) excretion. Fifteen kg of AgNP were added over two ice-free seasons to a lake at IISD-Experimental Lakes Area in Canada. We measured nitrogen, phosphorus, and Ag excretion rates and ratios by perch pre-, during, and post the AgNP addition phases in both the experimental lake and a reference lake four times over a 10-year period. We found that in Year 2 of AgNP addition, exposed perch P excretion rates and P:Ag excretion rates increased. However, our empirical P excretion rates in both lakes diverged from model-based predictions of perch P excretion rates, leaving the reasons for the increase in P excretion rates speculative. Nonetheless, Ag release by perch indicates that fish may contribute to legacy Ag contamination in aquatic ecosystems, thereby extending Ag exposure and uptake by aquatic organisms.